All your hydrangea questions are answered | Marianne Binetti
By MARIANNE BINETTI
Enumclaw Courier Herald Columnist
June 6, 2012 · Updated 4:27 PM
When June arrives you may notice your vegetable seedlings and annual plants experiencing a growth spurt. Just like a teenager, they now have a huge appetite so this is your reminder to fertilize. Roses and perennials also benefit from a feeding this month and if you still have not fertilized the lawn, make sure you do so early in the month before the hot weather arrives.
You should not feed clematis vines in bud or bloom. Clematis is the queen of all vines here in the Northwest and thrives in our cool summer weather but if you give clematis a big dose of plant food just as it starts to bloom it sometimes drops the flower buds before they open in a misguided effort to grow more foliage. Instead, pamper your clematis with an organic mulch placed on top of the roots but not quite touching the thin and delicate stems of this vine.
June also is the month to add more hydrangeas to your garden. These summer-blooming shrubs now come in a wider range of colors, sizes and flower types. Here are the most-asked questions about growing hydrangeas.
Q. How do I prune my giant hydrangea? I have figured out that when I prune my big leaf hydrangea back to keep it from blocking the front windows it punishes me and does not flower again for a couple of years. Right now I can tell there are flower buds at the end of some branches but this monster is over 5 feet tall and again blocking the window. R., email
A. I vote you move this hydrangea to a new spot where it can spread out its branches and grow into the full-bodied shrub it was meant to be. Replace this giant old-fashioned hydrangea with a dwarf or ever-blooming hydrangea that can be more easily kept under control. Hydrangeas are happiest when they are left to grow natural and never pruned. The new varieties like Endless Summer and Blushing Bride are an exception as you can cut back the branches on these hydrangeas in spring or summer and still get blooms; they will flower on new growth instead of two-year-old wood like traditional big leaf hydrangeas.
Q. I was given a beautiful pink hydrangea for Mother’s Day. It has unusual blooms that are more flat than the round ball hydrangea flowers. Do you know what type of hydrangea this is, can I plant it outside and will it survive the winter here and bloom again next year?
A. It sounds like you’ve received one of the new gift hydrangeas called Strawberries and Cream and the good news is it can go out into the garden in our climate for years of enjoyment. The flowers you describe are called “lace cap” as the center blooms do not open, giving the illusion of a lacy frill around a center cap of buds. Enjoy the blooms indoors but by June remove the plant from it’s pot and replant into a spot where it is protected from the hot afternoon sun. Hydrangeas love moist soil and newly-planted hydrangeas will need extra water the first summer and into the fall until they establish a strong root system. There’s no need to fertilize your newly-transplanted hydrangea as you want this greenhouse-grown plant to harden off or acclimate to the outdoor life. A mulch over the roots during the first winter will help it to survive and grow into a tough shrub that flowers each summer.
Q. I had a blue hydrangea but once I moved it closer to the house it turned more purple and almost lavender. Why do hydrangeas change from blue to pink? P.P., Enumclaw
A. Hydrangeas are the only shrub with such gender issues, coming out to the world blue in our naturally acid soil of western Washington. If you add lime around the roots of your big leaf hydrangeas the acidity of the soil and the flowers will change to pink or lavender depending on the amount of aluminum available in the soil. I suspect the gender confusion in your case is caused by the cement foundation of your house. Enough lime may have leached from the concrete to make the soil less acid, so the flower color changes. To feminize your blue hydrangeas you can add lime around the base of the shrubs. Start with just one-half cup of dolomite lime per plant as too much lime will turn the soil too alkaline and cause yellow leaves. Add aluminum sulfate to the soil to make it more acid and to keep your hydrangeas a more manly blue.
Marianne Binetti has a degree in horticulture from Washington State University and is the author of “Easy Answers for Great Gardens” and several other books. For book requests or answers to gardening questions, write to her at: P.O. Box 872, Enumclaw, 98022. Send a self-addressed, stamped envelope for a personal reply.
For more gardening information, she can be reached at her Web site, www.binettigarden.com.